The University of Córdoba Ankylosing Spondylitis Metrology Index (UCOASMI), a novel composite measure of mobility based on an automated motion-capture system (UCOTrack), demonstrated good construct validity and high clinical reproducibility, with excellent intra- and interobserver reliability. Findings from an observational study were reported in The Journal of Rheumatology.
The recently developed UCOTrack and UCOASMI, which produces vertebral and cervical mobility scores, have the potential to improve patient evaluation and enhance objective mobility measurements. Investigators sought to examine their reproducibility compared with other commonly employed measures.
An observational study at 3 centers enrolled 30 participants (mean age, 52.9 years; 73.3% men; mean disease duration, 25.9 years; mean Bath Ankylosing Spondylitis Disease Activity Index, 3.0). Participants were each tested twice (3-5 days apart) for intraobserver reliability, using UCOASMI, BASMI, and other validated instruments. To establish interobserver reliability, within 3 to 7 days of study initiation, 3 of 10 individuals from each hospital were also tested at the other 2 centers. The researchers then calculated intraclass correlation coefficients (ICC) to assess reliability.
Using a 0 to 10 scale, the mean UCOASMI score was 5.2 on the first visit. For both intra- and interobserver reliability, the UCOASMI yielded an ICC of 0.98, demonstrating very high reproducibility across testing days and centers. The minimal detectable change for UCOASMI was 0.74 points. Comparatively, the BASMI yielded ICCs of 0.91 and 0.83 for intra- and interobserver reliability, with a minimal detectable change of 0.82 points.
Other conventional metrology indicators produced lower but acceptable reproducibility, with a few exceptions. The intraobserver ICC of tragus-to-wall distance was only 0.30, and the interobserver ICC was 0.41 for lateral flexion, 0.61 for cervical rotation, and 0.07 for the Schöber test.
Study limitations included variability in results despite the use of an automated process. The researchers also note that additional intervening factors (patient height and pain, BASDAI score, location, time of day, temperature) may have affected the UCOTrack and UCOASMI measurements.
The researchers confirmed their hypothesis that the UCOASMI would yield good reliabilities, and compared with the BASMI, UCOASMI demonstrated excellent metrological stability and better evaluation of vertebral mobility. “These results suggest that the UCOTrack movement analysis is an advance in the functional assessment of axial spondyloarthritides,” observed the authors, adding, “We should bear in mind the longterm consequences of reduced mobility and the importance of both its periodic measurement and targeting when choosing therapy.” They recommended using the new technology in the future for patient monitoring and in further trials.
This study was funded by Merck Sharp & Dohme of Spain.
Disclosures: Dr L. Cea-Calvo and Dr M.J. Arteaga are full-time employees at Merck Sharp & Dohme of Spain. UCOTrack is owned by the University of Córdoba and the Andalusian Health Service.
Garrido-Castro JL, Curbelo R, Mazzucchelli R, et al. High reproducibility of an automated measurement of mobility for patients with axial spondyloarthritis [published online June 15, 2018]. J Rheumatol. doi: 10.3899/jrheum.170941